U.S. patent number 3,827,145 [Application Number 05/293,745] was granted by the patent office on 1974-08-06 for artificial tooth structure.
This patent grant is currently assigned to Plessey Handel und Investments A.G.. Invention is credited to Wilfred Arthur Richards.
United States Patent |
3,827,145 |
Richards |
August 6, 1974 |
ARTIFICIAL TOOTH STRUCTURE
Abstract
An artificial tooth comprising a crown section; a root section
adapted to be inserted into an alveolus in the jaw of a vertebrate,
the root section being formed by a member of a carbon material
which is microcrystalline in structure and substantially
impermeable and having at least one substantially cone-shaped
projection adapted to fit approximately within the inner surface of
the alveolus; and means resiliently securing the crown section to
the root section. The resilient securing means are arranged such
that they are capable of absorbing sudden shocks which might be
applied to the artificial tooth structure such as by biting upon
something unexpectedly hard.
Inventors: |
Richards; Wilfred Arthur (Much
Hadham, EN) |
Assignee: |
Plessey Handel und Investments
A.G. (Zug, CH)
|
Family
ID: |
10437327 |
Appl.
No.: |
05/293,745 |
Filed: |
September 29, 1972 |
Foreign Application Priority Data
|
|
|
|
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Sep 30, 1971 [GB] |
|
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45468/71 |
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Current U.S.
Class: |
433/175 |
Current CPC
Class: |
A61C
13/30 (20130101); A61C 8/0036 (20130101); A61C
8/0012 (20130101); A61C 8/0086 (20130101) |
Current International
Class: |
A61C
13/30 (20060101); A61C 8/00 (20060101); A61C
13/225 (20060101); A61c 013/00 () |
Field of
Search: |
;32/1A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Peshock; Robert
Attorney, Agent or Firm: Scrivener Parker Scrivener &
Clarke
Claims
What is claimed is:
1. An artificial tooth comprising a crown section; a root section
adapted to be inserted into an alveolus in the jaw of a vertebrate,
the root section being formed by a member of a carbon material
which is microcrystalline in structure and substantially
impermeable and having at least one substantially cone-shaped
projection adapted to fit approximately within the inner surface of
the alveolus; and means resiliently securing the crown section to
the root section, the resilient securing means including at least
one stub extension for the said member, the stub extension fitting
into a complementary cavity in the crown section; and an
elastomeric material interposed between the stub extension and the
wall of the cavity and between the lower surface of the crown
section and those regions of the upper surface of the said member
which surround the stub extension, the elastomeric material being
preformed and shaped to conform to the profile of the interface
between the crown section and the root section, each stub extension
having a bulbous head causing the preformed elastomeric material to
be in a state of compression and such that it effects a substantial
seal between the edge of the crown section and the root section.
Description
This invention relates to an artificial tooth structure based on an
implant to take the place of the root of an extracted tooth.
Dental implants for insertion into an alveolus in the jaw of a
vertebrate to form the root section of an artificial tooth are
described in our co-pending patent application Ser. No.
200,313.
A natural tooth is supported in the alveolus of the jaw bone by a
periodontal ligament which includes fibrous connecting tissue
extending between the cementum of the tooth root and the jaw bone
itself, which fibres are normally in tension.
The natural tooth is thus resiliently supported for a very limited
amount of movement in both horizontal and vertical directions and
is thus capable of absorbing sudden shocks which might be applied
to it such as by biting upon something unexpectedly hard.
With an artificial tooth structure which is based upon an implant,
it is known that a regular periodontal ligament forms about the
implant and tends to retain the implant in position within the
alveolus. It is, however, thought that the jaw bone growth which
occurs after implantation is a major contributory factor in implant
retention, therefore, the root section of an artificial tooth is
more rigidly attached to the jaw bone than the root section of a
natural tooth. The previously mentioned unexpected shocks which a
relatively rigid retained artificial tooth could be subjected to
might, especially with an implant of vitreous carbon, which is
itself a relatively brittle material, give rise to substantial
damage.
Carbon materials which are microcrystalline in structure and
substantially impermeable, for example those known as vitreous,
glassy and pyrolytic carbons are chemically, biologically and
physically compatible with animal tissue and are, therefore,
ideally suited for use in the fabrication of artificial tooth
structures.
This invention provides an artificial tooth comprising a crown
section; a root section adapted to be inserted into an alveolus in
the jaw of a vertebrate, the root section being formed by a member
of a carbon material which is microcrystalline in structure and
substantially impermeable and having at least one substantially
cone-shaped projection adapted to fit approximately within the
inner surface of the alveolus; and means resiliently securing the
crown section to the root section.
In one form the root section, which is of a carbon material such as
vitreous carbon that is microcrystalline in structure and
substantially impermeable, is provided with means for facilitating
the securing of the root section within the alveolus, and is
provided with one or more integral or attachable stub extensions,
the crown section being fastened to the or each stub extension by
an intermediate elastomeric material. The elastomer may be rubber
and may be preformed, and the stub extensions may have bulbous
heads so that as the crown is forced into position over such a head
or heads the elastomer is squeezed into a state of compression so
as to support the crown section of the artificial tooth in a
flexible manner, preferably comparable to the flexibility provided
by the natural periodontal ligament. In this case the amount and
shape of the elastomeric material may be so chosen and controlled
by moulding that sufficient of the elastomer is extruded by the
squeezing-on process to form a reasonable seal between the edge of
the crown section and the root section.
As an alternative arrangement the elastomer may be, for example, a
fast curling silicone rubber which is injected under pressure into
the space between the or each stub extension and the crown section,
the latter being supported by a jig type of device while curing
takes place.
The securing of the root section within the alveolus can be
effected by any one of the methods outlined in our co-pending
patent application Ser. No. 200,313.
The drawings show rather schematically a section in FIG. 1 of a
human tooth, this consists of a crown 1 of enamel supported by a
main body of dentine 2, which in the root portion is surrounded by
a layer of cementum 3. This root portion is supported in the
alveolar socket of the jaw bone 4 by fibrous material forming part
of the periodontal ligament and shown schematically by the fibres
5.
FIG. 2 shows a similar socket in which an implant 6 of for example
vitreous carbon, has been inserted, after extraction of the natural
tooth to form the root section of an artificial tooth.
This implant has grooves 7 running around its outer surface and
alveolar bundle bone 8 has grown into contact with the implant 6 so
as to hold it rigidly in the jaw bone.
The implant 6 has an integral stub extension 9 which has closely
controlled dimensions and which is non-circular. The head of the
stub projects only slightly beyond its neck and an artificial crown
section 10 of, for example, a plastics material, is provided with a
complementary cavity to fit over the stub with an intermediate
member 11 of an elastomeric material such as rubber. The volume of
the member 11 is chosen so that when the crown section 10 is forced
into position over the head of the stub 9 the elastomeric material
of the member 11 is caused to flow in a direction towards the
exterior of the artificial tooth. The lower edges of the cavity in
the crown section 10 are relieved as shown at 12 to accommodate the
elastomeric material of the member 11, which is caused to flow
outwards.
The elastomeric material which is trapped between the crown section
and the stub 9 is thus caused to be in compression as is the
remainder of the member 11 which lies between the upper shoulders
13 of the implant 6 and the lower surfaces of the crown section
10.
Thus, although the root section 6 of the artificial tooth is
rigidly held in the alveolus by the jaw bone growth, the crown
itself is, due to the resilient mounting provided by the member 11,
capable of limited flexibility in relation to the root section so
that the natural condition of a tooth is simulated and it is
enabled to accommodate itself to certain shock loads.
In order that the crown section may be successfully forced onto the
stub 9 without exerting too much pressure on the alveolar bone, the
crown section 10 may be provided with at least two lateral passages
such as the passage 14 in which levers may be inserted so as to
contact the lower side of the head of the stub 9 and enable the
crown section to be forced down into position against the forces
exerted by the member 11. After the crown section is in position
the passages 14 may be plugged with suitable material.
A further form of the invention is shown in FIG. 3, in which the
alveolus from which a natural tooth has been extracted, has had
inserted into it an implant 21. The gingival tissue 31 would have
been sutured over the implant 21 to hold it in position in a
preliminary healing period during which bundle bone 22 will have
grown inwards from the alveolar cavity into contact with the
implant 21 so as to enter its peripheral grooves and hold it firmly
in position in the alveolus.
The upper surface of the implant 21 is formed with a recess 23.
Preferably with roughened or grooved walls, and receives a peg
portion of a bulbous spigot 24. The peg portion of the spigot 24 is
secured in the recess of the implant 21 by a suitable cement 32.
The spigot 24 therefore provides a stub extension in the implant
21.
When the cement 32 is adequately set an artificial crown section 26
for example of acrylic resin, is placed over the bulbous portion of
the spigot 24, and is held in place by a somewhat flexible and
preformed basket-like member 27 which is previously inserted into a
cavity in the crown section 26 and which is shaped to conform to
the interface between the crown section 26 and the root section 21
and arranged to provide a space around the spigot 24 within the
cavity of the crown section 26. When the crown section 26 is thus
held in position a fast curing elastomeric material 28 such as for
example Dow Corning sealant is injected into this space through an
aperture 29 in the wall of the crown section 26 so as to fill the
space between the wall of the cavity of the crown section 26 and
the spigot 24 and so as to slightly exude therefrom around the
approximately annular gap between the lower edge of the crown
section 26 and the upper surface of the implant 21.
The gingival tissue 31 is shown for clarity spaced apart from the
implant 21 but after a further period of healing it will grow
inwards and the level of the joint between the crown section 26 and
the implant 21 is prefereably arranged such that after healing the
gingival tissue 31 will cover it.
The material and structure of the member 27 is such that it
provides sufficient friction to hold the crown section 26 in
position during the curing of the elastomeric material 28. The
member 27 may, for example, be moulded from polyvinylchloride, the
hardness of which may be suitably controlled by choosing the
proportion of plasticiser that it contains.
The dimensions of the bulbous spigot 24 which forms the stub
extension are accurately controlled as are those of the cavity
within the crown section 26 so as to define between them a space
which when fitted with the chosen elastomeric material 28 will
permit a degree of resilient movement of the crown section when in
use such as to cushion the implant 21 from damaging shock and the
bone of the jaw from unpleasant jarring.
The method outlined in preceding paragraphs in relation to FIG. 3
can be used for the root structure of FIG. 2 in order to secure the
crown section 10 to the integral stub extension 9 of the root
section 6.
This method of resiliently securing the root section to a crown
section has the advantage that fewer crown shapes and sizes need to
be stocked since the attitude and projection of the crown section
can, to some extent, be self-adjusting by contact with teeth in the
opposite jaw while curing of the elastomeric material is taking
place.
It is to be understood that the foregoing description of specific
examples of this invention is made by way of example only and is
not to be considered as a limitation in its scope.
* * * * *